[llvm] [Object] Provide operator< for ELFSymbolRef (PR #89861)

[Amir Ayupov via llvm-commits]

https://github.com/aaupov created https://github.com/llvm/llvm-project/pull/89861

Normally, operator< accepting DataRefImpl is used when comparing
SymbolRef/ELFSymbolRef. However, it uses std::memcmp which interprets
DataRefImpl union as char string. For ELFSymbolRef it's known that it
uses the struct view of the union, therefore a specialized operator< can
be used instead.

>From b6630e85ff5d4a35cf8d77fad63ba93791ffa806 Mon Sep 17 00:00:00 2001
From: Amir Ayupov <aaupov at fb.com>
Date: Tue, 23 Apr 2024 19:34:12 -0700
Subject: [PATCH] [Object] Provide operator< for ELFSymbolRef

Normally, operator< accepting DataRefImpl is used when comparing
SymbolRef/ELFSymbolRef. However, it uses std::memcmp which interprets
DataRefImpl union as char string. For ELFSymbolRef it's known that it
uses the struct view of the union, therefore a specialized operator< can
be used instead.
---
 llvm/include/llvm/Object/ELFObjectFile.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/llvm/include/llvm/Object/ELFObjectFile.h b/llvm/include/llvm/Object/ELFObjectFile.h
index 1d457be93741f2..8ec0e3fe15dc9d 100644
--- a/llvm/include/llvm/Object/ELFObjectFile.h
+++ b/llvm/include/llvm/Object/ELFObjectFile.h
@@ -199,6 +199,14 @@ class ELFSymbolRef : public SymbolRef {
   }
 };
 
+inline bool operator<(const ELFSymbolRef &A, const ELFSymbolRef &B) {
+  const DataRefImpl &DRIA = A.getRawDataRefImpl();
+  const DataRefImpl &DRIB = B.getRawDataRefImpl();
+  if (DRIA.d.a == DRIB.d.a)
+    return DRIA.d.b < DRIB.d.b;
+  return DRIA.d.a < DRIB.d.b;
+}
+
 class elf_symbol_iterator : public symbol_iterator {
 public:
   elf_symbol_iterator(const basic_symbol_iterator &B)